Fractal Rabbit
Explorer
By and large I don't I don't enforce alignment other my no evil PC policy. Alignment is just one more descriptor amongst many that help define a character.
Where I use it is in determining how NPCs and monsters respond, how they see the world. This is based on the psychology 101 class from long ago. The theory is that everyone views the world through frameworks and preconceptions. Two people can look at exactly the same situation and have vastly different opinions on what is going on. One person may see a beggar on the street and have empathy for someone down on their luck while another may see someone who is lazy or unwilling to work. Yet another person would see someone that could be abducted and killed and no one would notice.
As another example, a lawful person may look at how a kingdom is being ruled and see a tyranny where title, not worth determines a person's value. Another may look at the same kingdom and see an organized structure that works for the people by giving them a sense of tradition and a proper place.
There's a lot of leeway in this concept, they are just general guidelines. There may often be conflict - a Chaotic Good character may not like the tight control a king has over his kingdom, but may realize that the option is worse. A Lawful Evil person may work to throw a kingdom into chaos so that in the long term a new regime may rise from the ashes.
In addition, people aren't always 100% consistent. Personal experience may soften the heart of a chaotic evil serial killer for very specific individuals. A lawful good paladin may have a blind spot and not realize the harm they are doing to innocents.
This.
Do I enforce Alignment? That thought had never entered my head until I spoke with someone (read, argued vociferously) with someone at a con years ago. And I still don't consider it.
Alignment is my tool to help me figure out how deities, monsters and NPCs (i.e. The World) will interact with the PCs.
-Does a paladin behave in a way that will cause him/her to lose their powers?
-Does a party act like Murder Hoboes?
-How does a dragon respond to people skulking around the horde?
I will almost never tell someone the way I interpret their alignment. The exception being paladins and clerics, and that just as a possible warning, and that consequences may be imminent.
Otherwise, play your character how you see fit. The consequences are yours.